Change Over Time

Evolution: Change Over Time Age of earth 4.55 billion years (rocks dated on earth 3.8 to 3.9 billion by decay of their radioactive elements) Life began 3.9 to 4.1 billion years ago Life forms have evolved over a long period of time Great diversity of life, how did it arise how are things related?

Evidence-Organisms have changed over time Fossil Record- Organism is preserved (pg 382 and 417) Paleontologist: Scientist that studies fossils What does the fossil record show? The history of life on Earth, how different organisms have changed over time Extinct: Species die out (99% of all species has died out) Rock- Only hard parts of the organism are preserved for example bones; it is buried under layers of sediment. The minerals in the bones, calcium and hydroxyapatite, get replaced, one by one, with the minerals in the sediment.

Evidence of Change Over Time Fossil Record Archeopteryx 150-145 mya Tyrannosaurus rex 68-65 mya

Trilobites 17,000 species from 540-250 mya marine arthropods

Q. What type of rock do fossils usually occur in? Sedimentary rock Q. Give an example of an organism whose history is written in stone The horse Q. Where in the earth’s layers of rock would you expect to see the oldest life forms? In the lower layers (bottom)

Can see a change in life forms in the different layers of rock

The fossil record is incomplete; it does not show every step in the evolution of earth’s life forms. Q. Suggest reasons why this is the case. Not all organisms have hard parts. Location, sediment and other conditions have to be present to form a fossil. Exposure of fossil sites

Dating Fossils Relative: Estimate a fossils age by comparing its position in the rock layers compared to other fossils (index fossils) Index Fossil: easliy recognised, large range but short time period on Earth Radioactive dating: use of radioactive decay of certain elements. Decay is at a known constant rate known as a half-life Uranium-235 decays to lead 207 half-life is 700 mya Potassium-40 to argon-40 half-life = 1.26 billion years Carbon-14 to carbon-12 half life 5 568 yrs

Frozen- Organism has to be frozen quickly before any tissues start to decay. For example Iceman found in the Alps in 1991 was 5300 years old.

Amber- Organism gets caught in resin of ancient trees usually conifers, which then hardens to fossilize them

Using your text book research evidence that supports evolution, for each provide a description. 2. Biogeography

3. Comparative Anatomy Study of the organisms structure Scientists compare similarities and differences in organisms structure. Homologous structures have similar functions and origins, but are seen in different forms. Their similarities suggest a common (shared) ancestor. The differences are due to the different evolutionary paths, structures evolved to suit different environments and adapt that animal to a particular way of life.

Homologous Structures

Vestigial Structures

4. Comparative Embryology Comparing and contrasting the embryos of different organisms. Show relationships between species not always seen in the adult. Pig and human inherited the same basic body plan from a common ancestor.

Embryology

5. Molecular Biology Studies on a biochemical level, for example the structure of blood proteins hemoglobin are very similar in the human and the chimpanzee. The amino acid sequences are almost the same. Human and chimpanzee shared a common ancestor Analyzing similarities in DNA and RNA sequences (genes)  Genes are a basis for change. Rise of new alleles and genes by mutation give rise to new proteins, which enable an organism to change. A process of evolution.  

Molecular Clock